Re: Interaction between databse cache, DBWR and datafiles

"Rachel Wilson" <wilsonr_at_logica.com> wrote in message news:936259dc.0301300707.7d093fc2_at_posting.google.com...

I expect that you will get a clearer explanation from some of the educators on this list about the rest of this but i can offer two hopefully helpful remarks

> 4. if it isn't found, the block is read into the middle of the LRU
> list, or the MRU end, or the first free block from the LRU end
> depending on which document you read(?)

> it is step 4 that most troubles me as the documentation seems to
> contradict itself

Thats because it depends on (at least) what type of access you are doing. A FTS won't place its blocks at the MRU end of the list, whereas a access by rowid will. I suspect that the mechanism may be altered slightly fvor the kmeep and recycle pools (otherwise what's the point of the recycle pool at least).

>
> Also The other questions I can't answer by reading the documentation
> are:
> * Is a buffer "block sized" ie, one block per buffer?

Yes. As of 9i you can have multiple buffer caches - one for each block size that you use.

--
Niall Litchfield
Oracle DBA
Audit Commission UK